Effect Of Straw Modified Material On Control Of Potassium In The Sandy Soil

The sandy soil with loose soil particles has less structure, weak retention of water and fertility, so the productivity of it is low. Potassium is of great important in plant growth and metabolism, but its easy loss caused the low utilization of potassium fertilizer and increase agricultural inputs. Therefore, it is important to increase the content of potassium and improve the adsorption and fixation of potassium, as well as to enhance the utilization rate of potassium fertilizer and reduce its loss. In this study, biological pretreatment of straw, bentonite and PAM were made into straw modified material. The effect of straw modified material on control of potassium in the sandy soil was studied through culture experiment, isothermal adsorption-desorption experiment and leaching experiment. This research can provide theoretical basis for the application and extension of straw modified material in the future. The main conclusions are as follows:(1) Straw modified material could effectively increase the content of available potassium in the sandy soil. During the prior period of soil culture, the content of available potassium reduced with the increase of PAM of formula in the same application amount; while during the later period of soil culture, the regulation is contrary. After 60 days of soil culture, the content of available potassium of most treatment with straw modified material reached maximum and were 60.59%-217.96% higher than that of CK. During every culture period, different content of PAM of formula in the same application amount had weak effect on the content of available potassium in the sandy soil. The content of available potassium also increased with the increase of application amount in the same formula. The content was the highest when application amount was maximum, and on the contrary the lowest. During the four soil culture periods, the average content of available potassium improved 61.07%-78.88% when the application amount was A3 compared with that of A1. In every culture period, the application amount of the treatment with the highest content of available potassium in each formula was all A3 (10 g/kg). As the culture time prolonged, the content of available potassium of CK decreased, while the content of available potassium of the treatment with straw modified material was increased at first and then decreased, but increased in general. The content of available potassium of the treatment with straw modified material increased 6.32%-75.01% when the culture time was 60 days compared with that of 10 days.(2) The adsorption property to potassium in the sandy soil could be effectively improved by straw modified material. With the increase of PAM of formula in the same application amount, the average adsorption rate of potassium increased in general. In every culture period, the formula of the treatment with the highest average adsorption rate in each application amount was almost F3 (900:100:30). After 90 days culture, the average adsorption rate of most treatment with straw modified material reached maximum, and the average adsorption rate of T2,3, T5,3, and T10,3 increased by 10.32,14.67 and 15.28 percentage point respectively compared with that of CK. The application of PAM could significantly increase the adsorption of potassium in the sandy soil. The average adsorption rate of potassium increased with the increase of application amount when the formula was same. In every culture period, the application amount of the treatment with the highest average adsorption rate in each formula was almost A3 (10 g/kg). During the four culture periods, the average adsorption rate was 2.17-5.52 percentage point higher when the application amount was A3 compared with that of A1. Applying a lot of straw and bentcnite could effectively improve the adsorption property to potassium in the sandy soil. As the culture time prolonged, the average adsorption rate of CK decreased, while the treatment with straw modified material gradually increased. The average adsorption rate increased 3.67-10.10 percentage point when the culture time was 90 days compared with that of 10 days. It could well reflect adsorption reaction in the sandy soil using Langmuir equation, and correlation coefficients reached extremely significant level. In every culture period, applying straw modified materials could increase the maximum adsorption capacity, adsorption equilibrium constant and the maximum buffer capacity of potassium to some extent.(3) The average desorption rate of potassium in the sandy soil increased after applying straw modified materials. The variation regulation of average desorption rate in the sandy soil of different treatment was basically identical with that of average absorption rate, and the temporal variation regulation of different treatment was similar to that of the average adsorption rate. The average desorption rate of every treatment increased 1.92-7.89 percentage point compared with that of CK after 90 days culture. During the four culture periods, the average desorption rate increased 0.94-2.24 percentage point when the application amount was A3 compared with that of A1. The average desorption rate increased 1.34-6.41 percentage point when the culture time is 90 days compared with that of 10 days.(4) Straw modified material had a significant inhibitory effect on potassium leaching in the sandy soil. With the increase of PAM of formula in the same, the total leaching amount of potassium reduced. The formula of the treatment with the lowest total amount of leaching was F3 (900:100:30) under every application amount. The total leaching amount of T2,3, T5,3 and T10,3 decreased 7.82%, 24.90% and 48.00% separately compared with that of CK. When the formula was same, the total leaching amount of potassium reduced with the increase of application amount. The application amount of the treatment with the lowest total amount of leaching was A3 (10 g/kg) in each formula. The average total amount of leaching reduced 28.52% when the application amount was A3 compared with that of A1. The vertical migration of potassium in the sandy soil could be restrained by applying straw modified material. For the upper layer of soil, the content of available potassium of the treatment increased 12.46%-102.30% than that of CK; for the subsoil, the content of available potassium of the treatment decreased 7.51%-58.02% compared with that of CK.